New Zealand children are currently ranked the third most overweight and obese in the developed world. Further, differences by ethnic and socioeconomic factors are evident, with Māori and Pacific children, and the most deprived, being disproportionately impacted. Although much research has examined the association between watching television and childhood overweight/obesity, less is known about the effects of new media such as smart phones, tablets and iPods. Such research has primarily used self and proxy report, and researcher-observation to estimate children’s screen time. Wearable cameras have the potential to overcome some of the limitations of previous methods. This thesis aimed to determine the nature and extent of children’s screen time during the after school period on a typical weekday.

Methods

In 2014 and 2015, 169 children from Wellington schools wore cameras on a lanyard around their necks that took pictures every seven seconds for four days, as part of the Kids’Cam study. For this thesis (the Kids’Cam Screen Time study) Kids’Cam data available for the Thursday after school period was analysed. A study-specific annotation protocol and schedule was developed to guide the annotation of 120,780 images from 105 children (45 boys, 59 girls; 45 New Zealand European, 36 Māori and 24 Pacific) using bespoke annotation software, a process that took approximately 150 hours. Each image was reviewed for instances of a screen, and annotated for the setting, the type of screen and the activity being undertaken on the screen. Data were analysed using Stata to determine mean times and rates of screen time, and differences by gender, ethnicity and deprivation.

Results

Children had a mean screen time of 44 minutes, 52 seconds during the after school period. Rate for overall screen time was significantly greater in boys than girls. Overall screen time was greater in non-overweight children than overweight/obese.

Non-overweight children spent considerably more time using computers than overweight/obese children. As deprivation level increased there was a slight decrease in television use, with the exception of the least deprived children, who had the lowest rate of television use.

Of the activity categories included in the study, the highest mean screen time was watching programmes, followed by games and social activities. Non-overweight children spent significantly more time playing games, while overweight/obese children spent more time using screens for social activities. The rate of screen time was greater in boys than girls for all activities except for watching programmes. Rate of programmes and background television increased somewhat with increasing deprivation.

Conclusion

Wearable cameras are an effective research tool to investigate children’s screen time and the types of screens they use, due in part to their objective nature. Study findings suggest that the association between screen time and overweight/obesity in childhood is becoming more complex and that the association is perhaps limited to television. A small negative relationship suggests that new media may potentially be protective against overweight and obesity. The association observed between television use and overweight/obesity was substantially smaller than reported previously. This may be due to the changing nature of television watching. Multiple screen use may be a contributing factor to this observation, as children’s hands may be occupied by an additional screen, reducing the opportunity for snacking. This finding may also be due to an association between new media, and low deprivation. Kids’Cam Screen Time was limited to analysing the Thursday after school period only. The study was also limited by compliance of candidates, and the scope of what could be seen in the photos. To gain a better insight on the true association between children’s screen use and overweight and obesity, further research should determine screen use on other days of the week, especially the weekend, and over different time periods.

To ensure children are protected from harm from the use of screen, it is important they and their parents are aware of and practise healthy screen behaviours, and that governments ensure they are adequately informed of such behaviours. However, the findings of this study would suggest that interventions to address childhood obesity might be better concentrated on creating healthy food environments to support healthy food behaviours, than those addressing physical activity levels associated with screen time. Given the rising use of screens by children globally, the findings of this study are likely of interest in other countries.